Mike and Tripp were gracious enough to share several details of their rigging on their previous F18. Some of it pertains to this discussion.

I sail one of their old boats. My tack line pulls slack out of my spin sheet by way of a couple of rings at the back of the trampoline attached to that bunji on the tack line. When the spin is up, the bunji is slack and it lets the spin halyard free. When the spin goes down and the tack line pulls forward, it tensions the bunji and pulls the halyard back to the rear of the trampoline at two points.

http://www.microwindracing.com/boat.html